Investigation of reactivity and structure formation in a K–Te–U oxo-system under high-temperature/high-pressure conditions

Abstract

The high-temperature/high-pressure treatment of the K-Te-U oxo-family at 1100 °C and 3.5 GPa results in the crystallization of a series of novel uranyl tellurium compounds, K[(UO)(TeO)], K[(UO)TeO], α-K[(UO)TeO] and β-K[(UO)TeO]. In contrast to most of the reported uranyl compounds which are favorable in layered structures, we found that under extreme conditions, the potassium uranyl oxo-tellurium compounds preferably crystallized in three-dimensional (3D) framework structures with complex topologies. Anion topology analysis indicates that the 3D uranyl tellurite anionic framework observed in K[(UO)(TeO)] is attributable to the additional linkages of TeO polyhedra connecting with TeO disphenoids from the neighboring U-Te layers. The structure of K[(UO)TeO] can be described based on [UTeO] clusters, where six TeO polyhedra enclose a hexagonal cavity in which a UO polyhedron is located. The [UTeO] clusters are further linked by TeO square pyramids to form the 3D network. Similar to uranyl tellurates, both α-K[(UO)TeO] and β-K[(UO)TeO] contain TeO octahedra which share a common face to form a dimeric TeO unit. However, in α-K[(UO)TeO], these TeO units connect with UO tetragonal bipyramids to form a 3D structural framework, while in β-K[(UO)TeO], the same TeO dimers are observed to link with UO pentagonal bipyramids, forming 2D layers. Raman measurements were carried out and the vibration bands related to Te-O, Te-O and U-O bonds are discussed.

Structural and Spectroscopic Investigation of Novel 2D and 3D Uranium Oxo-Silicates/Germanates and Some Statistical Aspects of Uranyl Coordination in Oxo-Salts

“…29 For the U− As Recently, we found that high-temperature/highpressure conditions increase the diversity of U−Se/Te 4+ −O frameworks due to the variation of coordination geometries of Te 4+ and U 6+ . 33,34 The average CN of U for U−Se/Te 4+ −O family (5.04) is close to that for U−P/As 3+ −O, which is attributed to the same ionic potential (0.06) for both systems. By analyzing the coordination environments of uranyl ions in all known U 6+ −T−O phases, we found that the ionic potential of central cations T in oxo-anion groups in their higher oxidation states correlates to the CNs of uranyl ions in these materials.…”

“…Almost half of the structures for the U–Se/Te 4+ –O system have 5-coordinated uranyl, and structures of 10 phases possess mixed 4- and 5-coordinated and 5- and 6-coordinated uranyls. Recently, we found that high-temperature/high-pressure conditions increase the diversity of U–Se/Te 4+ –O frameworks due to the variation of coordination geometries of Te 4+ and U 6+ . , The average CN of U for U–Se/Te 4+ –O family (5.04) is close to that for U–P/As 3+ –O, which is attributed to the same ionic potential (0.06) for both systems.…”

Thorium Chemistry in Oxo-Tellurium System under Extreme Conditions

“…30 Under the extreme condition, the compounds tend to crystallize in unconventional structure types which are dramatically different from those synthesized via conventional high-temperature or hydrothermal conditions, as demonstrated in the high probability of noncentrosymmetric observed in the Na-U-Te oxo-system and the structural complexity of the K-U-Te group. 31 However, compared to the tremendous success achieved from the uranium oxo-tellurium family, very few details are known about the formation and crystal structures of thorium counterparts. The only representative in the thorium oxotellurium family with a refined crystal structure is ThTe 2 O 6 , which was obtained more than 30 years ago from a solid-state method at a temperature of 700 °C.…”

Achieving and Stabilizing Uranyl Bending via Physical Pressure

“…Examples of findings in this field are the reports of rich noncentrosymmetry in the Na−U−Te oxo-system 16 or increased atypical structure types with more complex structures and dimensionalities in the K− U−Te or K−U−Mo oxo-systems. 17 . 18 The title phase, Na 4 [(UO 2 )(SO 4 ) 3 ], was obtained under an extreme conditions study of the A I −U−S system (A I -alkali metals).…”

“…Our focus of the study was on investigating the phase formation behavior of actinide oxo-chalcogenates under high-temperature/high-pressure conditions. Examples of findings in this field are the reports of rich noncentrosymmetry in the Na–U–Te oxo-system or increased atypical structure types with more complex structures and dimensionalities in the K–U–Te or K–U–Mo oxo-systems .…”